The present invention relates generally to rechargeable battery cells and more particularly concerns a resealable vent for such a cell having a flat plastic case.
During recent years there has been a tremendous growth in the manufacture and use of miniature electronic devices such as hand-held calculators. Most of these devices are designed to operate on self-contained batteries in addition to be operable when plugged into a conventional electrical outlet, with or without an adapter. Many of the battery operated models utilize rechargeable batteries which, if properly and periodically recharged, last for long periods of time before replacement is required. However, one of the limitations on the physical design of hand-held calculators and the like which use rechargeable batteries has been the size and shape of conventional rechargeable batteries, most of which are cylindrical in shape, relatively space consuming, and housed in metal cases. Moreover, if either the shape or the material of the battery case is changed problems of case deflection and possible rupture due to internal pressure are encountered.
Accordingly it is the primary aim of the present invention to provide a resealable vent in a flat plastic case for a rechargeable battery cell.
A more specific object is to form such a resealable vent out of inexpensive materials which nevertheless provide for reliable venting when a predetermined internal pressure is reached.
It is a more detailed object to provide a resealable vent in a flat plastic battery cell case which also forms part of an internal restraint to prevent bulging or other deformation of the case upon a build-up of internal pressure within the case below venting pressure.